An herbicide is a compound which adversely controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating and dwarfing. The term "plant" refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" includes all phases of development from seed germination to natural or induced cessation of life.
Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.
A manufacturer of an herbicide generally recommends a range of application rates and concentrations calculated to maximize weed control. The range of rates varies from approximately 0.01 to 50 pounds per acre (0.0111 to 56 kilograms per hectare kg/ha!), and is usually in the range of from 0.1 to 25 pounds per acre (0.112 to 28 kg/ha). The term "herbicidally effective amount" describes an amount of an herbicide compound which adversely controls or modifies plant growth. The actual amount used depends upon several considerations, including particular weed susceptibility and overall cost limitations. 4-Benzoylisoxazole herbicide compounds have been described in U.S. Pat. Nos. 5,371,063, 5,371,064 and 5,374,606 and in European Patent Publication Nos. 0 418 175, 0 487 357, 0 527 036 and 0 527 037 all incorporated herein by reference. None of these documents however, disclose the advantages of a 3-alkanethio, or an oxidized form thereof, appended to the benzoylisoxazole ring. Surprisingly, the inventors of the instant application have found that the foregoing modification gives the compounds unexpected and advantageous selectivity.